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Prof. POLIDOR BRATU
President - General Director of the ICECON Research Institute for Construction Equipment and Technologies of Bucharest

Basic Info


Research Keywords & Expertise

0 Mechanical Systems
0 Mechanics
0 dynamic systems
0 dynamic machines
0 Civil engineering, roads and bridges

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Short Biography

Professor Polidor Bratu attended the bachelor's studies of the Constructions Technical University of Bucharest, which he graduated from in 1972. Meanwhile, he attended the courses of the Faculty of Physics in Bucharest. In 1980 he obtained the PhD in Technical Sciences at the Constructions Technical University, in the field of technical mechanics and vibrations. From 1972 to 1995 he worked with the Constructions Technical University as a University Professor and Scientific Researcher within the INCERC Construction Research Institute in Bucharest. Ever since 1995 and until the present moment he has been working as a full University Professor at the "Dunărea de Jos" University of Galați and as a President - General Director of the ICECON Research Institute for Construction Equipment and Technologies of Bucharest. Since 1998 he has been a member of the Romanian Academy of Technical Sciences and President of the "Technical Mechanics" department. Since 1994 he has been the President of the Romanian Society of Acoustics and Vibrations, and since 2010 has been the President of the Romanian Societies of Theoretical and Applied MecResearch and development scientific activity I. “Civil engineering, roads and bridges” II. “Industry and construction technology” III. ”Structural protection, resistance and stability. Human Personnel Protection” IV. "Physical, rheological and numerical modelling of the behaviour of composite materials, devices, processes and systems"

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Journal article
Published: 28 November 2020 in Symmetry
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All the installations, devices, and annexes within the laser and the gamma ray production system within the ELI-NP project from Magurele are installed on an inertial platform that weighs over 54,000 tons. The platform is made of concrete, is insulated from the outside environment, and is supported by spring batteries and shock absorbers. The flatness of this platform respects some very strict standards, and, taking into account the processes that take place on the platform, the transmission of the different trepidations of the environment to the inertial mass must be extremely low. For this reason, a static study and a vibration analysis of the platform, performed in this paper, are required. The static analysis verifies if the flatness of the platform can be observed in operating conditions, and the dynamic analysis verifies how excitations coming from the external environment can be transmitted to the measuring equipment. The finite element method is used both to determine the deformability of the concrete platform for different loads, placed at different points and to determine its eigenvalues and its eigenmodes of vibration. The obtained results are analyzed and constructive solutions are proposed to improve the realized system, through a judicious placement of the installations and the distribution of the masses on the platform.

ACS Style

Calin Itu; Polidor Bratu; Paul Nicolae Borza; Sorin Vlase; Dorin Lixandroiu. Design and Analysis of Inertial Platform Insulation of the ELI-NP Project of Laser and Gamma Beam Systems. Symmetry 2020, 12, 1972 .

AMA Style

Calin Itu, Polidor Bratu, Paul Nicolae Borza, Sorin Vlase, Dorin Lixandroiu. Design and Analysis of Inertial Platform Insulation of the ELI-NP Project of Laser and Gamma Beam Systems. Symmetry. 2020; 12 (12):1972.

Chicago/Turabian Style

Calin Itu; Polidor Bratu; Paul Nicolae Borza; Sorin Vlase; Dorin Lixandroiu. 2020. "Design and Analysis of Inertial Platform Insulation of the ELI-NP Project of Laser and Gamma Beam Systems." Symmetry 12, no. 12: 1972.

Conference paper
Published: 20 November 2020 in Springer Proceedings in Physics
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Buildings protection against seismic actions has, in recent times, led to an intense emulation of innovative solutions for the insulation of the base. Thus, under the new conditions of industrial development of antiseismic devices, at high and guaranteed performance level, dynamic isolation systems can be achieved resulting from assembling in various configurations of simple devices. In this context, the designers have, on the basis of the elastomeric antiseismic devices and the fluid dissipators, constructed individual units in a modular system. These, by installation-mounting in a sufficiently large number, are designed to provide the degree of dynamic isolation. In the present paper we present a modular E/(E − V) type Zener model, consisting of two elastomeric devices and a viscous damping fluidized dissipator. In order to isolate a building, a sufficient number of modules must be used to define in a unitary isolation system the base for a given building. Consequently, the paper will include the dynamic model based on Zener schematization of the entire isolation system and the specific parameters for calculating and evaluating the dynamic isolation level.

ACS Style

Polidor Bratu; Cristina Opriţescu; Amalia Ţârdea; Ovidiu Voicu; Adrian Ciocodeiu. Parametric Analysis of Dynamic Insulation in the Action of the Seismic Movements of the Base-Insulated Buildings. Springer Proceedings in Physics 2020, 367 -374.

AMA Style

Polidor Bratu, Cristina Opriţescu, Amalia Ţârdea, Ovidiu Voicu, Adrian Ciocodeiu. Parametric Analysis of Dynamic Insulation in the Action of the Seismic Movements of the Base-Insulated Buildings. Springer Proceedings in Physics. 2020; ():367-374.

Chicago/Turabian Style

Polidor Bratu; Cristina Opriţescu; Amalia Ţârdea; Ovidiu Voicu; Adrian Ciocodeiu. 2020. "Parametric Analysis of Dynamic Insulation in the Action of the Seismic Movements of the Base-Insulated Buildings." Springer Proceedings in Physics , no. : 367-374.

Journal article
Published: 29 September 2020 in Symmetry
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The dynamic model of the system of bodies with elastic connections substantiates the conceptual basis for evaluating the technological vibrations of the compactor roller as well as of the parameters of the vibrations transmitted from the vibration source to the remainder of the equipment components. In essence, the multi-body model with linear elastic connections consists of a body in vertical translational motion for vibrating roller with mass m1, a body with composed motion of vertical translation and rotation around the transverse axis passing through its weight center for the chassis of the car with mass m and the moment of mass inertia J and a body of mass m’ representing the traction tire-wheel system located on the opposite side of the vibrating roller. The study analyzes the stationary motion of the system of bodies that are in vibrational regime as a result of the harmonic excitation of the m mass body, with the force F(t)= m0rω2sinωt, generated by the inertial vibrator located inside the vibrating roller. The vibrator is characterized by the total unbalanced m0 mass in rotational motion at distance r from the axis of rotation and the angular velocity or circular frequency ω.

ACS Style

Polidor Bratu. Multibody System with Elastic Connections for Dynamic Modeling of Compactor Vibratory Rollers. Symmetry 2020, 12, 1617 .

AMA Style

Polidor Bratu. Multibody System with Elastic Connections for Dynamic Modeling of Compactor Vibratory Rollers. Symmetry. 2020; 12 (10):1617.

Chicago/Turabian Style

Polidor Bratu. 2020. "Multibody System with Elastic Connections for Dynamic Modeling of Compactor Vibratory Rollers." Symmetry 12, no. 10: 1617.

Journal article
Published: 22 September 2020 in Symmetry
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The variety of viscoelastic systems and structures, for the most part, is studied analytically, with significant results. As a result of analytical, numerical and experimental research, which was conducted on a larger variety of linear viscoelastic systems and structures. We analyzed the dynamic behavior for the viscoelastic composite materials, anti-vibration viscous-elastic systems consisting of discrete physical devices, road structures consisting of natural soil structures with mineral aggregates and asphalt mixes, and mixed mechanic systems of insulation of the industrial vibrations consisting of elastic and viscous devices. In this context, the compound rheological model can be schematized as being V-EV type of the Newton Voigt–Kelvin model with inertial excited mass, applicable to linear viscoelastic materials.

ACS Style

Cornelia Dobrescu. Dynamic Response of the Newton Voigt–Kelvin Modelled Linear Viscoelastic Systems at Harmonic Actions. Symmetry 2020, 12, 1571 .

AMA Style

Cornelia Dobrescu. Dynamic Response of the Newton Voigt–Kelvin Modelled Linear Viscoelastic Systems at Harmonic Actions. Symmetry. 2020; 12 (9):1571.

Chicago/Turabian Style

Cornelia Dobrescu. 2020. "Dynamic Response of the Newton Voigt–Kelvin Modelled Linear Viscoelastic Systems at Harmonic Actions." Symmetry 12, no. 9: 1571.

Journal article
Published: 23 June 2020 in Applied System Innovation
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The present paper addresses the problem of the dynamic response of a vibrating equipment for soil compaction. In essence, dynamic response vibrations are analysed by applying an inertial-type perturbing force. This is generated by rotating an eccentric mass with variable angular velocity, in order to reach the regime necessary to ensure the degree of compaction. The original character of the research is that during the compaction process, the soil layers with certain compositions of clay, sand, water and stabilizing substances change their rigidity and/or amortization. In this case, two situations were analysed, both experimentally and with numerical modelling, with special results and practical engineering conclusions, favourable to the evaluation of the interaction between vibrator roller–compacted ground. We mention that the families of amplitude–pulse and transmitted force–pulse response curves are presented, from which the dynamic effect in the compaction process results after each passage on the same layer of soil, until the necessary compaction state is reached.

ACS Style

Cornelia Dobrescu. The Dynamic Response of the Vibrating Compactor Roller, Depending on the Viscoelastic Properties of the Soil. Applied System Innovation 2020, 3, 25 .

AMA Style

Cornelia Dobrescu. The Dynamic Response of the Vibrating Compactor Roller, Depending on the Viscoelastic Properties of the Soil. Applied System Innovation. 2020; 3 (2):25.

Chicago/Turabian Style

Cornelia Dobrescu. 2020. "The Dynamic Response of the Vibrating Compactor Roller, Depending on the Viscoelastic Properties of the Soil." Applied System Innovation 3, no. 2: 25.

Journal article
Published: 15 August 2019 in Symmetry
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A comprehensive investigation, including analytical modelling, numerical analysis and experimental tests, has been carried out on many linear viscoelastic systems and structures. This approach is the result of research conducted by two research institutes, ICECON and INCERC Bucharest, from Romania. Thus, analyses were performed on the dynamic behaviour of composite viscoelastic materials, anti-vibration viscoelastic systems made of discrete physical devices, road structures consisting of layers of natural soil with mineral aggregates and asphalt mixtures, and mixed mechanic insulation systems for industrial vibrations formed of elastic and viscous devices. The objectives pursued were as follows: (a) providing a mass dosage of the mixture of earth (clay, sand, mineral aggregates, water, and stabilizer) in five variants; (b) carrying out a test run with a Bomag vibratory roller with variable vibration parameters; (c) Experimental evaluation of the vibration parameters and the force transmitted to the ground, correlated with the determination of the compaction layer; (d) use of methods of analysis for physic-mechanical and geotechnical parameters; (e) rheological and numerical modeling based on Zener schematics, so the consistency and veracity of the experimental data with the numerical simulation can be determined. Finally, a study is presented for a test track, where experimental and correlated input and response data are determined to validate the rheological model with a high loading rate.

ACS Style

Polidor Bratu; Cornelia Dobrescu. Dynamic Response of Zener-Modelled Linearly Viscoelastic Systems under Harmonic Excitation. Symmetry 2019, 11, 1050 .

AMA Style

Polidor Bratu, Cornelia Dobrescu. Dynamic Response of Zener-Modelled Linearly Viscoelastic Systems under Harmonic Excitation. Symmetry. 2019; 11 (8):1050.

Chicago/Turabian Style

Polidor Bratu; Cornelia Dobrescu. 2019. "Dynamic Response of Zener-Modelled Linearly Viscoelastic Systems under Harmonic Excitation." Symmetry 11, no. 8: 1050.

Journal article
Published: 02 March 2019 in Symmetry
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This paper presents the outcomes of the theoretical and experimental research carried out on a real model at natural scale using Voigt–Kelvin linear viscoelastic type m, c, and k models excited by a harmonic force F(t) = F0 sinωt, where F0 is the amplitude of the harmonic force and ω is the excitation angular frequency. The linear viscous-elastic rheological system (m, c, k) is characterized by the fact that the c linear viscous damping—and, consequently, the fraction of the critical damping ζ—may be changed so that the dissipated energy can reach maximum W d max values. The optimization condition between the W d max maximum dissipated energy and the amortization ζ 0 = ± ( 1 − Ω 2 ) / 2 Ω modifies the structure of the relation F = F(x), which describes the elliptical hysteresis loop F–x in the sense that it has its large axis making an angle less than 90° with respect to the x-axis in Ω < 1 ante-resonance, and an angle greater than 90° in post-resonance for Ω > 1 . The elliptical Q–x hysteretic loops are tilted with their large axis only at angles below 90°. It can be noticed that the equality between the arias of the hysteretic loop, in the two representations systems Q–x and F–x, is verified, both being equal with the maximum dissipated energy W d max .

ACS Style

Polidor Bratu. Hysteretic Loops in Correlation with the Maximum Dissipated Energy, for Linear Dynamic Systems. Symmetry 2019, 11, 315 .

AMA Style

Polidor Bratu. Hysteretic Loops in Correlation with the Maximum Dissipated Energy, for Linear Dynamic Systems. Symmetry. 2019; 11 (3):315.

Chicago/Turabian Style

Polidor Bratu. 2019. "Hysteretic Loops in Correlation with the Maximum Dissipated Energy, for Linear Dynamic Systems." Symmetry 11, no. 3: 315.